1. Field of the Invention
The present invention relates to a method and apparatus for cutting blanks from webs of material which are moved across a cutting region and cut by cutting means. More particularly, the method and apparatus permit the cutting out of patterns that cannot be fully accommodated within the cutting region during any single cutting step.
2. Background Art
In the past, in order to cut materials, for instance textiles, layers (sheets) of material had to be provided having at least the same length as the corresponding pattern to be cut out. In the clothing industry one works predominantly with a layer length (or cutting pattern length) of 4 to 7 meters, from which different patterns are then cut. In the upholstered furniture industry, layer lengths up to 15 meters are customary. The material layers, for example fabric layers, are laid out on pallets outside the cutting table by hand or by means of a laying machine. Then one individual pallet is placed on the cutting table and the cutting is effected by hand-guided cutting knives or an automatic cutting device (for instance a water-jet or laser-beam cutting device).
With this method the maximum possible cutting-pattern length is limited by the length of the cutting table.
For longer lengths it is known to provide rotating brushes on the cutting table which can transport a correspondingly longer pallet over the cutting table or through the actual cutting region.
It is quite common also to place several layers one on top of the other and cut them in one operation.
With both methods the fact must be borne in mind that the specific layer lengths must be longer, by a certain margin of safety (customarily 3 to 5 cm), than the length of the contours to be cut out. This is important in order to obtain a clean cutting line at the end of each individual contour, and furthermore to be able to take into account possible tolerances in connection with the placement of the individual layers on the pallets or the adjustment of the cutting tool.
Both methods have the disadvantage that long cycle times result from the placement of the layers on the pallets outside the cutting region. Also, the required margins of safety in each layer result, in general, in a large amount of waste. This not only increases the cost of manufacture but also, depending on the nature of the material used, results in some degree of pollution of the environment when the waste is disposed of.
Federal Republic of Germany AS 2,301,736 discloses an apparatus for cutting flat material with which a more streamlined manner of operation is possible. However, the method of cutting to be carried out with this apparatus has the disadvantage that the web of material is pushed forward by constant, identical distances regardless of the contour of the blank which is to be cut out. As a result, the machine has a long cycle time and a very great length.
Federal Republic of Germany OS 3,530,886 discloses a method for the automatic cutting of materials from a web of material. For this purpose there is used a cutting table having a cutting-material resting surface which is developed in brushlike manner and as an endless conveyor belt. The web of material, which can be withdrawn from a roll, is held on the cutting-material resting surface by a vacuum and cut. After a given length of cut has been effected, the cutting-material resting surface is transported further until the patterns which have been cut out can be removed.
This method can only be employed if the contour to be cut out is not larger than the distance from the place of cutting to the end of the cutting table. Furthermore, because the material is held by a vacuum, only a single-layer cut can be effected, which results not only in long cycle times but also in long setup times.
All prior art materials mentioned in this patent disclosure are expressly incorporated by reference.